There are many circumstances in which bones, bone fragments, or other tissue portions must be fused together, united, or otherwise permanently joined. Some examples include arthrodesis, corrective osteotomy, fracture, tear, or laceration. Bones, bone fragments, or other tissue portions heal better when they are stabilized with some mechanical load or stress across the discontinuity, for example when the bones, bone fragments, or other tissue portions are compressed together or distracted apart. This disclosure describes solutions to the problem of stabilizing bones, bone fragments, or other tissue portions while applying a therapeutic level of continuous mechanical load or stress across the discontinuity.